It's odd that our knuckles evolved in such a way that they can be cracked. What's happening that creates the sound of a knuckle cracking?

When you hear that distinct "pop" when you "crack" your knuckles, it's the result of nitrogen bubbles bursting in the synovial fluid in your joint. Once you crack your knuckles, it will usually take 20 minutes for the bubbles to form again so you can crack them again. Go ahead. Try it.

Asked by Tom Cohen · Last updated 5 years ago · 15.9K views